Process of making bituminous concrete pavements.



W. B. BRADY. PROCESS OF MAKING BITUMINOUS CONCRETE PAVEMENTS.

APPLICATION FILED JULY 14; 1911. 1,071,293..

Patented Aug. 26, 1913.

sita'rns PATENT ormon WILI-Lttll/E B. BRADY, 0F CHICAGQ, ILLINOIS, ASSIGNOB; OI! ONE-HELP T0 WILLIAM J; LANG, 0F GHIG'AGG; IIELINGIS.

PBOCESS OF MAKING- BITUMINOUSCGNCBEZCE-PAVEMENTS;

To all whom it may concern:

Be it known that I',.WILLIA1\[' B. BRADY,

a citizen of the- United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Processes of Making'. Bituminous Concrete Pavements, of

which the following. is aspecification; Y

This invention relates to an improved process of laying bituminous concrete pavement's, the process applying specifically to- Among the salient objects of the invention are-to providea method of laying pavement ofthecharacter'referred to which will insure rapid, economical and certain results, e., willinsurethemaking of uniformly good quality pavement ;'to provide a process which may be carried out chiefiy by the use of machinetools instead of requiring: much hand labor, and to provide'a process which enables the pavement to be readily made, which is characterized by extremedensity, imperviousness, and a reliable anchoring-ref the wearing surface as to'all' portions thereof to the foundation or sub-course.

The invention consists in-the matters hereinafter described, and more particularly pointed out in the appended claims.

The invention will be readily understood fromtlicfollowing description, reference being had to theaccompanying drawing, in.

which- 7 Figure 1 is a view n perspective with partsin cross section, of a portion of a pavement, embodying the invention; Fig. 2' a transverse sectional view showing the several'layers of the pavement, although it will be understood'that in practice each course is completed before the next is commenced.

in constructinga preferred embodiment of my' invention, the roadway to be im-' proved is first graded'to provide a uniform or substantially uniform surface, say, for

ordinary roads, about eight inches below 7 Specification of Letters Patent.

Application filedJ lay-1411911.

Patented Aug. 2d, 1913.

Serial No. 638,456.

the finished grade line. Upon the sub-grade thus prepared there is evenly laid or spread a foundation course of ordinary hydraulic cement concrete which is preferably madeof adepth about five'and one-halt inches and 1s called'the' foundation course, This foundation course is designated 1 in the drawing, and its constituents may be varied to suit local conditions; the? object being to provide a comparatively inexpensive rigid concrete-foundation; bviously this may ordinarily be" most economically obtained by'the'use of mineral aggregate graded-from relatively large" down to comparatively fine particles, the grading being in accordance with well-known practice for securing density of aggregate, or, in other wdrds,

elimination of'voids, and therefore the use of a minimum amount of cement proper.

Over this foundation course of concrete,

preferably before the same has set, there is evenly laid or'spread What I' term a slush coat 2 about one-half inch in depth, and composed of fine or comparatively line hydraulic concrete. A suitable formula for this slush coat is one part Portland cement (b -measure), three parts clean sharp sand (by measure),tlioroughly mixed into mortar by the addition of sullicient water and a thorough mixing; the mortar thus made being. applied immediately upon the foundation course while the same is still wet, so that goodunion is securedbetween the slush coat and the foundation course;

As soon'as tlie'slush coat has been evenly spread out over the foundation course, and before it has set or hardened, there is scatlei-ed and distributed evenly over the'whole a coating of broken stone, as 3, preferably sharp hard limestone, trap rock, or other. suitable stone, ranging from inch to 2' inches in diameter, and consisting prefer ably in the main of stone about one inchin' stones down until practically every individual stone is inset into the slush coat and so that in the main these stones are brought into bearing with the foundation course. This method of construction produces an anchoring surface to which the bituminous concrete is subsequently anchored. That is to say, the loose stones, larger in diameter than the thickness of the slush coat, are forced into the latter as to their lower portions and project freely above the slush coat, formin projections, angles and recesses with w ich the lower part of the wearing surface combines and anchors.

After the anchor surface has been applied and the slush coat allowed to set and dry out, the'bituminous concrete wearing surface 4 is applied. A preferred way of forming and applying the wearing surface is as follows; Over the anchor concrete surface there is poured and Spread a suitable asphaltic or bituminous binder, in quantities sufiicient to fill all voids in the surface of the anchor concrete and to fully submerge the anchor projections. This bituminous binder is, of course, preferably applied hot. Thereafter there is evenly spread a layer' of clean crushed limestone screenings, or granite screenings, washed torpedo sand, or other suitable mineral top dressing material, to a depth of about one inch in thickness, after which thistop dressing is thoroughly rolled and bonded into the bitumen. Thereafter all loosescreenings or top dressing material which has not been forced into and become bonded into the bitumen is swept off and a so-called squeegee coat of hot liquid asphalt or other suitable bitumen is applied-in quantities of about two hundred pounds to one hundred square yards of pavement. Thereafter the loose screenings which have been swept ofi"; andv if necessary additional loose screenings of the same character, are again spread over the surface of the pavement to a depth of one-fourth inch, and these screenings or top dressing material again rolled into and bonded with the bitumen, thereby producing the finishing or surfacing coat 5.

'While the above described manner-of preparing the bituminous concrete wearing surface is deemed the preferred way, it is nevertheless obvious that the bituminous concrete might be separately compounded of suitably graded mineral and bitumen before being spread, after being thoroughly mixed, and while hot, spread and rolled in a man ner entirely familiar to those skilled in the art. In either event it will be obvious that the bituminous concrete completely fills the interstices and depressions of the rough anchor surface and becomes perfectly bonded to the latter. By reason of the rigidly held anchor projections rising from the concrete foundation into the bituminous concrete wearing surface, it will be obvious that the latter is prevented from being laterally displaced or flowing, even under very heavy trafiic or in extremely warm weather. Nevertheless the wearing surface is entirely water-proof, and because of the stability afforded by the anchor foundation, the consistency of the bituminous binder may be safely kept comparatively soft, 71. 6., slightly softer than would be safe to use in a wearing surface composed wholly of bituminous concrete and not combined or incorporated with an anchor supporting surface. The advantage of employing bituminous binder which is not too hard is, of course, well understood, and resides chiefly in the freedom from liability to crumble and crack, especially in cold weatheror after a long period of time.

While the foregoing description sets forth the exact method which in practice I have found to be preferred, yet it'will be understood that the method may be somewhat modified without departing from the invention. The appended claims, therefore, are not to be construed specifically, except in so far as they are made specific in terms.

I claim as my invention:

1. The herein described method of laying pavement which consists in first laying a relatively heavy sub-course of hydraulic ce ment and suitably finishing the surface thereof to leave the same uniform and smooth, or approximately 50, then applying and uniformly spreading a relatively thin course of fine hydraulic cement, then, while said latter course is still plastic, distributing uniformly over the same an anchor course of nn'neral aggregate composed of pieces of stone of greater diameter than the thickness of said course of plastic cement, and pressing the coarse aggregate down into bearing \vitlrthe foundation course, thereby embedding it in said plastic course, allowing the thus-formed anchor course to set and harden, and finally applying a wearing surface course of bituminous concrete over the anchor course and suitably rolling and finishingthe same.

2. The herein described method of laying pavement which consists in first preparing the bed, next laying thereon a relatively heavy sub-course of coarse mineral aggregate mixed with hydrauliccement and suitably rolling, compacting and finishing'the surface thereof so as to leave the same uniform and approximately smooth, then applying and uniformly spreading a thin coat of fine hydraulic semi-liquid cement, then, while said latter coat is still plastic, dis tributing over the same in anchor course of mineral aggregate largely composed of pieces of stone of greater diameter than the thickness of sald course of plastic cement,

and rolling or otherwise pressing'the same merge the anchor projections of the anchor into the plastic cement and into bearing with course and suitably rolling and finishing the sub-course, allowing the thus-formed ansaid. wearing course.

chor course of coarse aggregate and plastic WILLIAM B. BRADY. cement to set and harden, and finally apply- Witnesses: j

ing a Wearing surface of bituminous con- ALBERT H. GRAVES,

crete of such thickness as to completely sub- EMILE Rosn. 

